The present invention relates to methods, systems and components thereof for delivering pharmaceutical substances to patients for imaging procedures and, more particularly, for delivering radiopharmaceuticals to patients for positron emission tomography (PET) or single-photon emission computerized tomography (SPECT) procedures.
PET and SPECT are noninvasive, three-dimensional, imaging procedures that provide information regarding physiological and biochemical processes in patients. PET and SPECT images of, for example, the brain or another organ, are produced by injecting the patient with a dose of a radiopharmaceutical (using, for example, fluid delivery systems such as those disclosed in U.S. Pat. No. 6,767,319, JP Publication Nos. 2000-350783 and 2002-306609 and PCT Publication Nos. WO 2004/091688, WO 2006/007750 and 2004/004787, the disclosures of which are incorporated herein by reference) and then creating an image based on the radiation emitted by the radiopharmaceutical. The radiopharmaceutical generally includes a radioactive substance, such as a radioisotope, that can be absorbed by certain cells in the brain or other organs, concentrating it there.
Radioisotopes, especially those with short half-lives, can be relatively safely administered to patients in the form of a labeled substrate, ligand, drug, antibody, neurotransmitter or other compound or molecule that is normally processed or used by the body (for example, glucose). The radioisotope acts as a tracer of specific physiological or biological processes. For example, fluorodeoxyglucose (FDG) is a normal molecule of glucose, the basic energy fuel of cells, to which is attached a radioisotope or radioactive fluor (i.e., F-18). The F-18 radioisotope is produced in a cyclotron equipped with a unit to synthesize the FDG molecule.
Cells (for example, in the brain) that are more active in a given period of time after an injection of FDG will absorb more FDG because they have a higher metabolism and require more energy. The F-18 radioisotope in the FDG molecule experiences a radioactive decay, emitting a positron. When a positron collides with an electron, annihilation occurs, liberating a burst of energy in the form of two beams of gamma rays in opposite directions. The PET scanner detects the emitted gamma rays to compile a three dimensional image.
To allow for cell uptake of the radiopharmaceutical, the patient typically rests for a period of time (45-90 minutes for FDG) after the radiopharmaceutical is injected. After sufficient time for cell uptake has elapsed, the patient is typically placed on a movable bed that slides into the PET (or SPECT or other suitable) scanner. The PET scanner includes several rings of radiation detectors. Each detector emits a brief pulse of light every time it is struck with a gamma ray coming from the radioisotope within the patient's body. The pulse of light is amplified, by for example a photomultiplier, and the information is sent to the computer for forming images of the patient.
To minimize the radiation dose to patients, radiopharmaceuticals containing radioisotopes, such as Flourine-18, Technetium-99, Carbon-11, Copper-64, Gallium-67, Iodine-123, Nitrogen-13, Oxygen-15, Rubidium-82, Thallium-201, Chromium-51, Iodine-131, Iodine-151, Iridium-192, Phosphorus-32, Samarium-153, and Yttrium-90, having relatively short half-lives are typically used for PET and SPECT imaging procedures and other radio-therapies. F-18, for example, has a half-life of 109.7 minutes.
Because of its short half-life, the radioactivity level of the radioisotope will quickly decrease after it is manufactured in a cyclotron or a reactor. Consequently, the elapsed time (and corresponding decrease in radioactivity level of the radioisotope) after synthesis of the radiopharmaceutical must be factored into calculating the volume of radiopharmaceutical required to be injected into the patient to deliver the desired radioactivity dose. If the time delay after synthesis is long in relation to the radioisotope's half-life or if the calculated volume of radiopharmaceutical to be injected into the patient is insufficient to deliver the desired radioactivity dose, the delivered radioactivity dose may be too low to provide diagnostic-quality images, resulting in wasted time and effort and exposing the patient and medical personnel to unnecessary radiation.
Further, long-term radiation exposure to technologists and other personnel working in the scanner room can pose a significant health risk. Although the half-life of the radiopharmaceutical is rather short and the applied dosages are considered an acceptable risk to the patient, under current procedures administering personnel are exposed each time they work with the radiopharmaceuticals and other contaminated materials, such as tubing and syringes, used to inject the radiopharmaceuticals into patients. Constant and repeated exposure over an extended period of time can be harmful.
A number of techniques are used to reduce radiation exposure to medical personnel, including minimizing the time of exposure of personnel, maintaining distance between personnel and the source of radiation and shielding personnel from the source of radiation. In general, the radiopharmaceuticals are typically delivered to a nuclear medicine hospital suite or other medical facility from a radiopharmaceutical synthesis facility (within or outside the hospital or medical facility) equipped with a cyclotron in, for example, a lead-shielded container (often called a “PIG”). Often, the radiopharmaceutical is manually drawn from such containers into a shielded syringe. See, for example, U.S. Pat. No. 5,927,351, disclosing a drawing station for handling radiopharmaceuticals for use in syringes. Remote injection mechanisms can also be used to maintain distance between the operator and the radiopharmaceutical. See, for example, U.S. Pat. No. 5,514,071, disclosing an apparatus for remotely administering radioactive material from a lead encapsulated syringe. Nevertheless, these current procedures and systems still result in unnecessary and repeated exposure of technicians and other medical personnel to radiation.
It has long been recognized as very desirable to develop devices, systems, components and methods for calculating and delivering accurate and effective doses of radiopharmaceuticals to patients, while reducing the exposure of administering or other medical personnel to such hazardous pharmaceuticals.